Mitt Romney has ended months of speculation by naming Paul Ryan as his vice-presidential running mate ahead of the November election.

The 42-year-old Wisconsin Representative was unveiled in Norfolk, by the presumptive Republican presidential candidate ahead of a four-day bus tour through key states and battlegrounds.

Appearing alongside Ryan for the first time, and with the World War II battleship, the USS Wisconsin in the background, Romney called his VP pick a “shining exception” in Washington, and praised Ryan’s “character and values”.

“Paul Ryan works in Washington but his roots remain in Janesville, Wisconsin,” said Romney to the delight of the flag-waving crowd, adding that youthful-looking Representative had become the “intellectual leader of the Republican Party.”

The selection of Ryan, revealed by Huffington Post late on Friday night, will be seen as a gamble by Romney, who is hoping that the Representative’s appeal to fiscal conservatives on the right of the GOP, as well as the Tea Party base, will out-way the loss of any moderate Republicans or Independent voters at the polls.

John McCain’s 2008 presidential campaign was hugely energised by his selection of Sarah Palin as VP candidate, even if the bounce was only temporary. By selecting Ryan, Romney is betting on a similar boost for a campaign that has come under increasing criticism in recent weeks, not only from Democrats, but from allies within his on party.

In the run-up to Saturday’s announcement, a number of “safer” candidates had been mooted, from Minnesota Governor Tim Pawlenty to Ohio Senator Rob Portman.

Yet by selecting Ryan, the Chairman of the House Budget Committee and the architect of the Path To Prosperity series, Romney is pushing the economy front and centre of his presidential campaign.

Romney’s VP candidate has built his name in recent years on the back of the “Ryan Budget”, a series of radical proposals for the US economy that includes repealing much of the Patient Protection and Affordable Care Act (Obamacare), while converting Medicare – the safety net offering seniors access to health care via the state – into a voucher-style system dispensed from government through private insurance companies.

Ryan’s selection will be hugely popular with the conservative wing of the GOP, as well as the Tea Party grass roots, many of who see the repeal of Obamacare and the end to entitlement spending as the key focus of the 2012 election.

Yet Ryan is likely to prove equally as popular with Democrats, who now have the Republican’s poster boy for fiscal conservatism in their sights. Should Obama and Biden defeat Romney and Ryan in November, it would be a resounding rejection of the principles upon which much of the Tea Party has campaigned since 2009, as well as clear rejection of the path of austerity and deficit reduction as favoured by the Romney camp.

Ryan’s budget, particularly the reformation of Medicare, one of the government’s most popular programmes, will give Democratic campaigners another easy line of attack, while large spending cuts, allied to income tax rate reduction, can easily be portrayed as a budget for the wealthy at the expense of the middle and working classes.

And while Romney has been quick to point out Obama’s lack of experience in the private sector, Democrats can now point to Ryan, whose career has been almost exclusively in politics.